The present invention relates to an improved pluggable electronic module configured to connect and/or convert data signals from a first serial transmission medium to a second serial transmission medium. A preferred embodiment of the invention relates particularly to an improved GigaBaud Interface Converter (GBIC) as defined by the GBIC specification, the teaching of which is hereby incorporated herein by reference. However, the improvements disclosed in this specification are applicable to high speed data communication modules other than GBICs as well.
The GBIC specification was developed by a group of electronics manufacturers in order to arrive at a standard small form factor transceiver module for use with a wide variety of serial transmission media and connectors. The specification defines the electronic, electrical, and physical interface of a removable serial transceiver module designed to operate at Gigabaud speeds. A GBIC provides a small form factor pluggable module which may be inserted and removed from a host or switch chassis without powering off the receiving socket. The GBIC standard allows a single standard interface to be changed from a first serial medium to an alternate serial medium by simply removing a first GBIC module and plugging in a second GBIC having the desired alternate media interface.
The GBIC form factor defines a module housing which includes a first electrical connector for connecting the module to a host device or chassis. This first electrical connector mates with a standard socket which provides the interface between the host device printed circuit board and the module. Every GBIC has an identical first connector such that any GBIC will be accepted by any mating GBIC socket. The opposite end of the GBIC module includes a media connector which can be configured to support any high performance serial technology. These high performance technologies include: 100 Mbyte multi-mode short wave laser without OFC; 100 Mbyte single-mode long-wave laser with 10 km range; Style 1 intracabinet differential ECL; and Style 2 intracabinet differential ECL.
The GBIC module itself is designed to slide into a mounting slot formed within the chassis of a host device. The mounting slot may include guide rails extending back from the opening in the chassis wall. At the rear of the mounting slot the first electrical connector engages the mating socket which is mounted to a printed circuit board within the host device. The GBIC specification requires two guide tabs to be integrated with the electrical connector. As the connector is mated with the socket, the guide tabs of the connector engage similar structures integrally formed with the socket. The guide tabs are to be connected to circuit ground on both the host and the GBIC. The guide tabs engage before any of the contact pins within the connector and provide for static discharge prior to supplying voltage to the module. When the GBIC is fully inserted in this manner, and the connector fully mated with the socket then only the media connector extends beyond the host device chassis.
Copper GBICs allow the host devices to communicate over a typical copper serial transmission medium. Typically this will comprise a shielded cable comprising two or four twisted pairs of conductors. In such GBICs, the media connector will generally be a standard DB-9 electrical connector, or an HSSDC connector at each end. In the case of copper GBICs this DB-9 or HSSDC connector is a purely passive device and serves no other function than to connect electrical signals between the cable and the GBIC module. Thus, it may be desirable to eliminate the media connector altogether, and directly attach two copper GBICs, one at each end of the copper cable, thereby eliminating two connectors and reducing the cost of the data link. It may be further desired to make such direct attach copper GBICs field installable such that the transmission cable may be routed and installed prior to attaching the GBIC modules. Such field installable GBICs would help reduce the risk of damage to the modules while the wiring is being installed.
In designing GBIC modules, a factor which must be considered is that GBICs are high frequency devices designed to operate at speeds above 1 Gigabit per second. Thus, the modules carry the potential of emitting high frequency signals to the surrounding area which may adversely affect sensitive equipment situated nearby. Therefore, a sophisticated shielding mechanism is required in order to prevent such unwanted emissions. In prior art modules, this has generally included a metallized or metal clad portion of the module located adjacent the media connector. The metal portion is configured to engage the chassis wall of the host device when the module is fully inserted into the mounting slot. The metallized portion of the module and the chassis wall form a continuous metal barrier surrounding the mounting slot opening. The metal barrier blocks any high frequency emissions from escaping from the host chassis due to a gap between the GBIC module and the chassis mounting slot. A disadvantage of prior art GBIC modules, however, is that spurious emissions are free to escape the module directly through the media connector. This leakage has the potential of disrupting the operation of nearby devices. The problem is most acute in so called xe2x80x9ccopper GBICsxe2x80x9d where an electrical connector is provided as the media connector. Furthermore, most prior art GBIC modules are formed of a plastic outer housing which allows EMI signals generated by the GBIC to propagate, freely within the chassis of the host device. These emissions can interfere with other components mounted within the host chassis and can further add to the leakage problem at the media end of the GBIC module.
Therefore, what is needed is an improved high speed pluggable communication module having an improved media connector end which acts to block all spurious emissions from escaping beyond the module housing. Such an improved module should be adaptable to function as a Giga-Bit interface converter module and interface with any GBIC receptacle socket. In such a module, the host connector should conform to the GBIC specification, and include the requisite guide tabs connected to the circuit ground. At the media end of the module, the improved module may include either an DB-9 style 1 copper connector, an HSSDC style 2 copper connector, or an SC duplex fiber optic connector as the second end media connector. Alternately, the module may provide for the direct attachment of the module to a copper transmission medium such that a single shielded copper cable may be interconnected between two host devices with an individual GBIC connected at each end. It is further desired that the module include plastic latching tabs to affirmatively lock the module into a corresponding host socket. Internally, the module should contain whatever electronics are necessary to properly convert the data signals from the copper transmission medium of the host device to whichever medium is to be connected to the media end of the module. In the case of GBIC modules, all of the operating parameters as well as mechanical and electrical requirements of the GBIC specification should be met by the improved module. However, though it is most desired to provide an improved GBIC module it must be noted that the novel aspects of a transceiver module solving the problems outlined above may be practiced with high speed serial modules other than GBICS.
In light of the prior art as described above, one of the main objectives of the present invention is to provide an improved small form factor interface module for exchanging data signals between a first transmission medium and a second transmission medium.
A further object of the present invention is to provide an improved small form factor interface module configured to operate at speeds in excess of 1 Giga-Bit per second.
Another objective of the present invention is to provide an improved interface module to prevent spurious electromagnetic emissions from leaking from the module.
Another objective of the present invention is to provide an improved interface module having a die cast metal outer housing including a ribbon style connector housing integrally formed therewith.
Another objective of the present invention is to provide an improved interface module having a die cast metal outer housing including detachable insulated latch members for releasably engaging a host device socket.
Another objective of the present invention is to provide an improved interface module having a die cast metal outer housing with an integrally cast electrical connector, including guide tabs electrically connected to the circuit ground of the module and configured to engage similar ground structures within a host device socket.
Still another objective of the present invention is to provide an improved Giga-Bit Interface Converter (GBIC) having a media connector mounted remote from the GBIC housing.
An additional objective of the present invention is to provide an improved GBIC having a shielded cable extending from the module housing, with the cable shield being electrically connected to the housing in a manner which electromagnetically seals the end of the module housing.
A further objective of the present invention is to provide an improved GBIC having a remote mounted media connector comprising a DB-9 connector.
A still further objective of the present invention is to provide an improved GBIC having a remote mounted media connector comprising an HSSDC connector.
Another objective of the present invention is to provide an improved GBIC having a remote mounted media connector comprising an SC duplex optical transceiver.
Another objective of the present invention is to provide an improved GBIC module having a flexible shielded cable extending therefrom, and a second GBIC module being connected at the remote end of the cable wherein the two GBIC modules are field installable.
All of these objectives, as well as others that will become apparent upon reading the detailed description of the presently preferred embodiment of the invention, are met by the Improved High Speed Interface Converter Module herein disclosed.
The present invention provides a small form factor, high speed serial interface module, such as, for example, a Giga-Bit Interface Converter (GBIC). The module is configured to slide into a corresponding slot within the host device chassis where, at the rear of the mounting slot, a first connector engages the host socket. A latching mechanism may be provided to secure the module housing to the host chassis when properly inserted therein. It is desirable to have a large degree of interchangeability in such modules, therefore across any product grouping of such modules, it is preferred that the first connector shell be identical between all modules within the product group, thus allowing any particular module of the group to be inserted into any corresponding host socket. It is also preferred that the first connector include sequential mating contacts such that when the module is inserted into a corresponding host socket, certain signals are connected in a pre-defined sequence. By properly sequencing the power and grounding connections the module may be xe2x80x9cHot Pluggablexe2x80x9d in that the module may be inserted into and removed from a host socket without removing power to the host device. Once connected, the first connector allows data signals to be transferred from the host device to the interface module.
The preferred embodiment of the invention is to implement a remote mounted media connector on a standard GBIC module according to the GBIC specification. However, it should be clear that the novel aspects of the present invention may be applied to interface modules having different form factors, and the s cope of the present invention should not be limited to GBIC modules only.
In a preferred embodiment, the module is formed of a two piece die cast metal housing including a base member and a cover. In this embodiment the host connector, typically a D-Shell ribbon style connector, is integrally cast with the base member. The cover is also cast metal, such that when the module is assembled, the host end of the module is entirely enclosed in metal by the metal base member, cover, and D-Shell connector, thereby effectively blocking all spurious emissions from the host end of the module.
A printed circuit board is mounted within the module housing. The various contact elements of the first electrical connector are connected to conductive traces on the printed circuit board, and thus serial data signals may be transferred between the host device and the module. The printed circuit board includes electronic components necessary to transfer data signals between the copper transmission medium of the host device to the transmission medium connected to the output side of the module. These electronic components may include passive components such as capacitors and resistors for those situations when the module is merely passing the signals from the host device to the output medium without materially changing the signals, or they may include more active components for those cases where the data signals must be materially altered before being transmitted via the output medium.
In a further preferred embodiment. a portion of the printed circuit board extends through the cast metal D-Shell connector. The portion of the printed circuit board extending into the D-Shell includes a plurality of contact fingers adhered thereto, thereby forming a contact support beam within the metal D-Shell. Additional guide tabs extend from the printed circuit board on each side of the contact beam. The guide tabs protrude through apertures on either side of the D-Shell. A metal coating is formed on the outer edges of the guide tabs and connected to the ground plane of the printed circuit board. The guide tabs and the metal coating formed thereon are configured to engage mating structures formed within the host receiving socket. and when the module is inserted into the host receiving socket, the guide tabs act to safely discharge any static charge which may have built up on the module. The module housing may also include a metal U-shaped channel extending from the front face of the D-Shell connector adjacent the apertures formed therein, the channel forming a rigid support for the relatively fragile guide tabs.
Again. in an embodiment, an interface converter module includes a die cast metal base member and cover. Both the base member and the cover include mutually opposing cable supports. Each cable support defines a semicircular groove having a plurality of inwardly directed teeth formed around the circumference thereof. The opposing cable supports of the cover align with the corresponding cable supports of the base member. Each pair of opposing cable supports thereby form a circular opening through which a flexible shielded cable may pass, and the inwardly directed teeth formed within each groove engage the cable and secure the cable within the module. Furthermore, the outer layer of insulation of the cable may be stripped away such that a portion of the metallic shield is exposed. When stripped in this manner, the cable may be placed within the module with the outer layer of cable insulation adjacent a first and second pair of cable supports and the exposed shield portion of the cable adjacent a third and fourth pair of cable supports. The teeth of the first and second pair of cable supports compress the outer layer of insulation and secure the cable within the module. Similarly, the teeth of the third and fourth cable supports engage the exposed metal shield, thereby forming a secure electrical connection between the cast metal module housing and the cable shield. In order to ensure a secure connection with the cable shield. the radii of the semicircular grooves and the third and fourth cable supports are reduced to match the corresponding reduction in the diameter of the cable where the insulation has been stripped away. Further, the insulation of the individual conductors may be stripped such that the bare conductors may be soldered to individual solder pads formed along the rear edge of the module""s printed circuit board.
In a similar embodiment, the module is made field installable. Rather than being soldered to the printed circuit board, the individual conductors may be connected utilizing an insulation displacement connector (IDC) mounted to the printed circuit board. In this embodiment the housing cover includes an IDC cover mounted on an inner surface of the cover. When the module is assembled, the IDC cover forces the individual conductors of the flexible cable onto knife contacts within the IDC connector. The knife contacts cut through the conductor""s insulation to form a solid electrical connection with the copper wire within.
A media connector is attached at the remote end of the flexible shielded cable. The media connector may be configured as any connector compatible with the high performance serial transmission medium to which the module is to provide an interface. In the preferred embodiments of the invention, these connectors include a standard DB-9 connector or an HSSDC connector for applications where the module is interfacing with a copper transmission medium, or may include an SC duplex optical transceiver for those cases where the interface module is to interface with a fiber optic medium. Within the housing the various conductors comprising the flexible shielded cable are connected to the printed circuit board and carry the serial data signals between the remote media connector and the module. In an alternate configuration, the length of the flexible cable is extended and a second interface module substantially identical to the first module is connected to the remote end of the cable.
In another embodiment, the module includes a plastic housing having a metallized or metal encased end portion. The housing includes a first end containing a discrete host connector. The conductive portion of the housing is configured to engage the perimeter of the mounting slot in the metal chassis of the host device which receives the module. This metal to metal contact forms a continuous metal barrier against the leakage of spurious emissions. The conductive portion of the housing includes the end wall of the module housing opposite the end containing the connector. This end wall at the second end of the housing includes a small circular aperture through which a short section of a flexible shielded cable protrudes. The flexible cable includes a plurality of individual conductors which may be connected to electrical circuits formed on the printed circuit board, and the cable shield bonded to the conductive portion of the housing. In a first preferred embodiment the cable comprises a four conductor shielded cable and in an alternative embodiment an eight conductor shielded cable is provided.
Thus is provided an adapter module for transmitting serial data signals between a first transmission medium and a second transmission medium. The module is defined by an electromagnetically sealed housing having first and second ends. The housing may be formed of die cast metal. The first end of the housing has a first connector attached thereto, which may be integrally cast with a base member of the housing. A flexible cable extends from the second end of the housing. The flexible cable includes a metallic shield which is bonded to the housing in a manner to electromagnetically seal the second end of the housing, thereby preventing high frequency electro-magnetic emissions from escaping the housing. Individual conductors within the cable are connected to circuits mounted on a printed circuit board contained within the housing. Finally, a media connector is mounted at the remote end of the flexible cable for connecting to an external serial transmission medium.